The first 3 pages of cylinder zero of a CP volume, have specific, non-page,
applications.
Obviously, page 0, contains the volume label. Page 1 and 2 have the CP
Allocation map (the map that shows what each cylinder can be used for...temp,
page, spol, perm, etc).
It use to be, I don't know if it is the case now, that the paging subsystem,
used all pages of the cylinder marked as PAGE. If it used page 0 or 1, there
went your volume header and page allocation map. No big deal as these are
stored in memory on a running system. But once you IPL, and CP tried to read
these pages.....
Back in the 2314 days, we sweated every cylinder. Now, we only sweat on a pack
basis. <G>
Just lay off cylinder 0 on any volume that isn't just attached to a guest.
Tom Duerbusch
THD Consulting
>>> Edward M Martin <[EMAIL PROTECTED]> 11/14/2008 9:56 AM >>>
Hello Everyone,
Just been following this thread. Could some one explain why
Cylinder 0 should not be defined as page?
Ed Martin
Aultman Health Foundation
330-588-4723
ext 40441
-----Original Message-----
From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] On
Behalf Of Mike Walter
Sent: Friday, November 14, 2008 9:50 AM
To: [email protected]
Subject: Re: Risk of Adding a Paging Volume
No matter. No harm would be done.... CPFMTZA wouldn't execute anyway.
;-)
Besides, cyl 0 as PAGE would not cause a failure, it's just not "best
practices".
Mike Walter
Hewitt Associates
